ONE THOUSAND YEARS OF COPPER MINING IN FALUN, CENTRAL SWEDEN, AND ITS EFFECTS ON LAKE ACIDITY

One thousand years of copper mining in Falun, central Sweden, and the resultant emissions of sulfur dioxide and heavy metals, has affected the acidity and pollution status of the surrounding landscape. Analyses of diatoms in sediment cores from 14 lakes within a 17 km radius of the mine show that, despite the large historical deposition of sulfur, there has only been a small decrease in pH in some of the lakes, typically from 6.5 to 6. Lakes started to acidify during the 17th century when Falun supplied 2/3 of the world copper production. Acidification may have been counteracted by effects of land-use changes following the expanding mining industry. Since the 17th century copper production and therefore sulfur emissions, have declined. Despite one hundred years of significantly reduced sulfur deposition, the diatom record shows no recovery in pH. Recovery may be hindered by changes in forestry in the area over the past 100 years. This study points to the importance of land-use for the acidity status of lakes. Land-use can either counteract acidification or alternatively delay recovery.